The invention relates to a compressed air supply system for a commercial vehicle. The system includes a compressed air inlet that can be coupled to a compressor, a filter unit that is coupled to the compressed air inlet via a delivery line, a discharge valve element that is coupled to a discharge outlet and the delivery line, an energy saving control outlet that can be coupled to a control inlet of the compressor, a delivery line shut-off valve element interposed between the compressor and the filter unit and a first valve element and a second valve element. The discharge valve element, the energy saving control outlet, the regeneration of the filter unit and the delivery line shut-off valve element are controllable by the valve elements.
The invention furthermore relates to a method for operating a compressed air supply system. The system including a compressed air inlet that can be coupled to a compressor, a filter unit that is coupled to the compressed air inlet via a delivery line, a discharge valve element that is coupled to a discharge outlet and the delivery line, an energy saving control outlet that can be coupled to a control inlet of the compressor, a delivery line shut-off valve element interposed between the compressor and the filter unit and a first valve element and a second valve element, provision being made, within the scope of the method, for the discharge valve element, the energy saving control outlet, the regeneration of the filter unit and the delivery line shut-off valve element to be controlled by the valve elements.
In utility or commercial vehicles, compressed air supply systems of this kind perform numerous functions. These include, especially, supplying the brake system and other compressed air consumers with dry, cleaned compressed air, providing a multi-circuit protection valve function to safeguard various consumer circuits from one another, to ensure a particular filling sequence and to provide a pressure regulator function. The compressed air used by the compressed air consumers is supplied primarily by a compressor, which is generally driven by the internal combustion engine of the utility vehicle. In many systems, the compressor can be transferred to an energy saving state, either by opening a clutch via which the compressor can be coupled to the internal combustion engine, or by pneumatic activation of a compressor control inlet in order to transfer the compressor to an idling state. Energy saving measures of this kind can also be assisted by ensuring that the operating sequences in the compressed air supply system take place as far as possible in such a way that compressed air, once produced, is not lost unnecessarily. At the same time, it should be noted that a certain loss of compressed air is unavoidable since the filter unit of the compressed air supply system must be repeatedly regenerated. For this purpose, dry compressed air from the compressed air tanks connected to the compressed air supply system is passed through the filter unit in the opposite direction to the direction of delivery. The air flowing through the filter unit at least partially absorbs the moisture in the filter unit and then flows out into the open via the discharge valve of the compressed air supply system.
In certain prior-art systems, provision is made to couple the energy saving operating state to the opening of the discharge valve, that is to say whenever the compressor is transferred to an energy saving state the discharge valve is opened too, resulting in an unnecessary loss of pressure in the entire delivery line ahead of a check valve facing the consuming units, which is arranged downstream of the filter unit.
EP 1 318 936 B1 describes a compressed air supply system provided with a regeneration function and an energy saving outlet to transfer a compressor to an idling state. Two solenoid valves are provided to provide these functions. Here, provision is made for the opening of the regeneration air path to be coupled to the opening of the discharge valve. In this way, the compressed air from the volume between the discharge valve and a check valve facing the consuming units, which is arranged downstream of the filter unit, is lost only if this is inevitable owing to the required regeneration. However, no measures are taken to conserve the compressed air in a delivery line between the compressor and the compressed air supply system during the regeneration phases. If this could be achieved by means of an elegant piece of circuit engineering, there would be an additional way of saving compressed air and hence energy.
The object on which the invention is based is to provide a compressed air supply system and an operating method which have a high potential for saving energy and exhibit an increase in functionality over the prior art.
The invention builds on the generic compressed air supply system in that the energy saving control outlet can be controlled by the first valve element, and the discharge valve element and the regeneration of the filter unit can be controlled by the second valve element, and in that the delivery line shut-off valve element is closed during the regeneration phase of the filter unit and can be transferred to an opened control state when not in the regeneration phase and when the discharge valve element is closed and the energy saving control outlet is supplied with air. Shutting off the line between the compressor and the filter unit by means of the delivery line shut-off valve element during the regeneration phase has the effect that the volume of compressed air between the compressor and the delivery line shut-off valve element is not lost during regeneration. Thus, essentially, the only compressed air which is lost to the atmosphere is that which is actually needed for regeneration and has flowed through the filter unit for this purpose. Outside the regeneration phase, it is possible, in particular, for there to be two different operating states of the compressed air supply system, namely the operating state for delivery and a state in which neither regeneration nor delivery takes place. In the last-mentioned phase, it is useful to transfer the delivery line shut-off valve element at least temporarily to an open control state in order in this way to prevent the delivery line and/or the delivery line shut-off valve element from freezing at low temperatures. This possibility is provided by the present invention.
In particular, it is envisaged that, in a first control state, the first valve element vents the energy saving control outlet, and, in a second control state, supplies the energy saving control outlet with air, and in that a compressor coupled to the energy saving control outlet can be transferred to an energy saving state by supplying the energy saving control outlet with air. The first valve element is thus provided exclusively for controlling the compressor.
In the context of the abovementioned configuration with regard to the first valve element it is envisaged, in particular, that, in a first control state, the second valve element vents a control inlet of the discharge valve element and a control inlet of the delivery line shut-off valve element, and blocks a regeneration air path, and, in a second control state, supplies air to the control inlet of the discharge valve element and the control inlet of the delivery line shut-off valve element and opens the regeneration air path, and that the discharge valve element is closed when the control inlet is vented and open when the control inlet is supplied with air, and the delivery line shut-off valve element is open when the control inlet is vented and closed when the control inlet is supplied with air. The second valve element thus operates both the discharge valve element and the delivery line shut-off valve element. Moreover, the regeneration air path is opened or blocked. This is possible because the discharge valve must always be open during regeneration and the delivery line should always be shut off to conserve compressed air. Activation of these components with a single valve element, namely the second valve element, is thus particularly economical.
It is useful if, in a first operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its first control state, resulting in an operating state for delivery. The discharge valve is closed, the regeneration path is blocked, the delivery line shut-off valve element is open and the compressor delivers. A pressure build-up thus takes place in the compressed air supply system.
It is furthermore envisaged that, in a second operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its second control state, resulting in an operating state for regeneration. With the regeneration path opened, the discharge valve element opened, the delivery line shut-off valve element closed and a compressor in the energy saving state, it is possible to carry out regeneration with an advantageous saving of energy, the energy saving being achieved, on the one hand, by the switching of the compressor to the idling phase and, on the other hand, by the conservation of the volume of compressed air in the delivery line.
It is furthermore preferred that, in a third operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its first control state, resulting in a blocking operating state with an open delivery line shut-off valve element. The shut-off valve is closed and the compressor is in its idling state. Regeneration does not take place during this blocking operating state. However, it is ensured that the delivery line shut-off valve element is open in order to prevent freezing of this element at low temperatures, and of the delivery line connected thereto.
According to a further embodiment of the present invention, it is envisaged that, in a first control state, the first valve element vents the energy saving control outlet, and vents a first control inlet of the delivery line shut-off valve element, and, in a second control state, supplies the energy saving control outlet with air and supplies the first control inlet of the delivery line shut-off valve element with air, and that a compressor coupled to the energy saving control outlet can be transferred to an energy saving state by supplying the energy saving control outlet with air, and the delivery line shut-off valve element is open when the first control inlet is vented and is closed under certain conditions when the first control inlet is supplied with air. In contrast to the embodiment described above, the first valve device now operates not only the energy saving control outlet but also the delivery line shut-off valve element.
In this case, it is useful if, in a first control state, the second valve element vents a control inlet of the discharge valve element and blocks a regeneration air path, and, in a second control state, supplies the control inlet of the discharge valve element with air and opens the regeneration air path, and if the discharge valve element is closed when the control inlet is vented and is opened when the control inlet is supplied with air. Since the first valve element actuates the delivery line shut-off valve element, it is sufficient that the second valve element should open and block the regeneration path and actuate the discharge valve.
It is useful if, in a first operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its first control state, resulting in an operating state for delivery. The discharge valve is closed, the delivery line shut-off valve element is opened, the regeneration path is opened and the compressor delivers.
Another possibility is one in which, in a second operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its second control state, resulting in an operating state for regeneration. The regeneration path is opened and the discharge valve is open. The compressor is in the idling state and the delivery line shut-off valve element is closed.
Another possibility is one in which, in a third operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its first control state, resulting in a blocking operating state. Outside the regeneration phase, the discharge valve remains closed, and the compressor can operate in its idling state if there is no requirement for compressed air.
A useful possibility in connection with this blocking operating state is one in which a third valve element is provided which, in a first control state, vents a second control inlet of the delivery line shut-off valve element and, in a second control state, supplies the second control inlet of the delivery line shut-off valve element with air, and in which the delivery line shut-off valve element is open when the second control inlet is supplied with air, even if the first control inlet of the delivery line shut-off valve element is supplied with air, with the result that, in the case of a third valve element, the system is in the blocking operating state with the delivery line shut-off valve element closed in the first control state and open in the second control state. The third valve element thus determines whether the delivery line shut-off valve element is open or closed in the blocking operating state, that is to say when the discharge valve is closed and the compressor is not delivering. Since the opening of the delivery line shut-off valve element is intended to prevent freezing of the valve element and of the connected line, it is possible to dispense with such opening, for example, when the temperatures are sufficiently high.
It is furthermore preferred if, in a fourth operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its second control state, resulting in an operating state for purging. In this operating state, the discharge valve element and the delivery line shut-off valve element are open in the delivery phase of the compressor. As a consequence, air can be delivered directly from the compressor to the discharge point of the compressed air supply system.
It is useful to provide for the third valve element to be coupled to a control line, via which further control functions can be implemented in the compressed air supply system. In accordance with the above embodiments, the third valve element is provided to close the delivery line shut-off valve element when required. Since this will only be necessary in certain operating states of the compressed air supply system, the compressed air to be controlled by the third valve element can also be used for other functions without impairing the energy saving functions described.
By way of example, provision can be made for the control line to be connected to a control inlet of an overflow valve which supplies a consumer circuit. The overflow valves of the compressed air supply system form a multi-circuit protection valve element which, on the basis of the opening and closing pressures assigned to the overflow valves, ensures a certain filling sequence and safeguarding of the individual consumer circuits from one another. Since an overflow valve of this kind can now be activated by the third valve element, it is possible to exert a direct influence on the functionality of the multi-circuit protection valve.
In this context, provision can be made for opening of the overflow valve to be assisted by supplying air to the control inlet. This enables a consumer circuit that is per se to be filled with a low priority to be filled preferentially in a selective manner. In particular, the circuit concerned can be the compressed air circuit assigned to the pneumatic suspension system of the vehicle or some other circuit which can be filled without sacrificing safety even when the available brake pressure is still inadequate. It is likewise possible to keep the overflow valves connected to the control line permanently open, thereby avoiding closure of the overflow valves when the pressure falls below the closing pressure.
According to another concept, a closed state of the overflow valve can be brought about and maintained by supplying air to the control inlet. This makes it possible, in particular, to separate a faulty circuit from the other circuits, making it possible to continue operating the compressed air system in the range of its optimum operating pressures without said system losing pressure via the faulty circuit.
It is useful if the valve elements are 3/2-way valves. This makes it possible to provide the connections and control states required for the functionalities described.
In particular, provision can be made for an electronic control unit to be provided, and for the valve elements to be solenoid valves. In this way, the various operating states of the compressed air supply system can be adopted on the basis of intelligent calculations, it being possible, in particular, to take into account numerous items of information relating to the utility vehicle. These can be made available directly or via a data bus to the electronic control unit, it being possible, in particular, for various control units of the utility vehicle to be connected to a data bus in order in this way to exchange information with the control unit of the compressed air supply system.
Provision can furthermore be made for the discharge valve element to be a 2/2-way valve. It is likewise useful for the delivery line shut-off valve element to be a 2/2-way valve.
The invention builds on the method of the generic type by means of a method in which the energy saving control outlet is controlled by the first valve element, and the discharge valve element and the regeneration of the filter unit are controlled by the second valve element, and in which the delivery line shut-off valve element is closed during the regeneration phase of the filter unit and is transferred to an opened control state when not in the regeneration phase and when the discharge valve element is closed and the energy saving control outlet is supplied with air. In this way, the advantages and special features of the compressed air supply system according to the invention are also utilized in the context of a method. This also applies to the particularly preferred embodiments of the method according to the invention which are given below.
In a useful development of said method, the first valve element vents the energy saving control outlet in a first control state and supplies the energy saving control outlet with air in a second control state, and a compressor coupled to the energy saving control outlet can be transferred to an energy saving state by supplying the energy saving control outlet with air.
Another possibility is that, in a first control state, the second valve element vents a control inlet of the discharge valve element and a control inlet of the delivery line shut-off valve element and blocks a regeneration air path and, in a second control state, supplies the control inlet of the discharge valve element and the control inlet of the delivery line shut-off valve element with air and opens the regeneration air path, and that the discharge valve element is closed when the control inlet is vented and is opened when the control inlet is supplied with air, and the delivery line shut-off valve element is opened when the control inlet is vented and closed when the control inlet is supplied with air.
It is preferred that, in a first operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its first control state, resulting in an on-load operating state.
It is furthermore preferred that, in a second operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its second control state, resulting in an operating state for regeneration.
It is furthermore useful if, in a third operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its first control state, resulting in a blocking operating state with the delivery line shut-off valve element open.
According to another embodiment of the method according to the invention, in a first control state, the first valve element vents the energy saving control outlet, and vents a first control inlet of the delivery line shut-off valve element, and, in a second control state, supplies the energy saving control outlet with air and supplies the first control inlet of the delivery line shut-off valve element with air, and a compressor coupled to the energy saving control outlet can be transferred to an energy saving state by supplying the energy saving control outlet with air, and the delivery line shut-off valve element is open when the first control inlet is vented and is closed under certain conditions when the first control inlet is supplied with air.
In this context, it is useful if, in a first control state, the second valve element vents a control inlet of the discharge valve element and blocks a regeneration air path, and, in a second control state, supplies the control inlet of the discharge valve element with air and opens the regeneration air path, and in that the discharge valve element is closed when the control inlet is vented and is opened when the control inlet is supplied with air.
It is furthermore provided that, in a first operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its first control state, resulting in an operating state for delivery.
It is furthermore preferred if, in a second operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its second control state, resulting in an operating state for regeneration.
It is also preferred if, in a third operating state of the compressed air supply system, the first valve element assumes its second control state and the second valve element assumes its first control state, resulting in a blocking operating state.
It is furthermore advantageous that a third valve element is provided which, in a first control state, vents a second control inlet of the delivery line shut-off valve element and, in a second control state, supplies the second control inlet of the delivery line shut-off valve element with air, and that the delivery line shut-off valve element is open when the second control inlet is supplied with air, even if the first control inlet of the delivery line shut-off valve element is supplied with air, with the result that, in the case of a third valve element, the system is in the blocking operating state with the delivery line shut-off valve element closed in the first control state and open in the second control state.
The invention can furthermore be configured in such a way that, in a fourth operating state of the compressed air supply system, the first valve element assumes its first control state and the second valve element assumes its second control state, resulting in an operating state for purging.
Provision can furthermore been made for the third valve element to be coupled to a control line, via which further control functions can be implemented in the compressed air supply system.
The method according to the invention is advantageously developed if the control line is connected to a control inlet of an overflow valve which supplies a consumer circuit. It is furthermore useful that opening of the overflow valve is assisted by supplying air to the control inlet. Provision can also be made for a closed state of the overflow valve to be brought about and maintained by supplying air to the control inlet.
It is furthermore advantageous that the valve elements are activated by an electronic control unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.